The Marano and Grado Lagoon is well known for being contaminated by mercury (Hg) from the Idrija mine (Slovenia) and the decommissioned chlor-alkali plant of Torviscosa (Italy). Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments (up to 6.81 μg/g) showed a slight variability with depth, whereas the highest methylmercury (MeHg) values (up to 10 ng/g) were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally (from 0.1 and 17% of dissolved Hg (DHg)) with the highest concentrations in summer. DHg diffusive effluxes higher (up to 444 ng/m2/day) than those reported in the open lagoon (~95 ng/m2/day), whereas DMeHg showed influxes in the fish farm (up to −156 ng/m2/day). The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.
Evaluation of mercury biogeochemical cycling at the sediment–water interface in anthropogenically modified lagoon environments
Elisa Petranich;Stefano Covelli
;Alessandro Acquavita;Marco Contin
2018-01-01
Abstract
The Marano and Grado Lagoon is well known for being contaminated by mercury (Hg) from the Idrija mine (Slovenia) and the decommissioned chlor-alkali plant of Torviscosa (Italy). Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments (up to 6.81 μg/g) showed a slight variability with depth, whereas the highest methylmercury (MeHg) values (up to 10 ng/g) were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally (from 0.1 and 17% of dissolved Hg (DHg)) with the highest concentrations in summer. DHg diffusive effluxes higher (up to 444 ng/m2/day) than those reported in the open lagoon (~95 ng/m2/day), whereas DMeHg showed influxes in the fish farm (up to −156 ng/m2/day). The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.File | Dimensione | Formato | |
---|---|---|---|
Petranich_et_al_2018_SI_JES.pdf
Accesso chiuso
Descrizione: articolo principale
Tipologia:
Documento in Versione Editoriale
Licenza:
Copyright Editore
Dimensione
3.07 MB
Formato
Adobe PDF
|
3.07 MB | Adobe PDF | Visualizza/Apri Richiedi una copia |
1-s2.0-S1001074217322970-mmc1.doc
Accesso chiuso
Descrizione: Supplementary tables
Tipologia:
Altro materiale allegato
Licenza:
Copyright Editore
Dimensione
68.5 kB
Formato
Microsoft Word
|
68.5 kB | Microsoft Word | Visualizza/Apri Richiedi una copia |
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.